The file extension is the (usually) three-letter abbreviation at the end of the file name.
Computers have led to a lot of changes in the music industry, creating new ways for music to be produced, distributed, stored and played. As digital music files come from a variety of sources, those sources can either use one of the popular file formats or create their own specific format for the music files, to align them with that company's software and/or device for playing them.
Common
MP3 (.mp3) is the most commonly used and widely supported audio file format, to the point where the term has become shorthand for audio files in general. It is a lossy file format, which means a good amount of (mostly inaudible) data is lost in the compression process. WAV (.wav), a similar format, is short for Waveform Audio File, and is more often seen on PCs than Macs. Similar commonly used formats and extensions include AAC (.aac, or Advanced Audio Coding) and CDA (.cda, or Compact Disc Audio) which is the format used by commercially produced CDs, and only contains the data for the tracks of the CDs, not the audio itself.
Apple
Apple has developed a number of different audio file formats and extensions, mainly in connection with their iTunes multimedia player/manager software and iPod portable media players. Among those are Apple Lossless (.m4a), which, as its name implies, uses lossless compression, as does AIFF (.aif or .aiff), which delivers CD-quality audio. M4P (.m4p) is used for audio files purchased from the iTunes Music Store, containing copyright protection to hamper file sharing. Apple also has a separate format for iPhone ringtones purchased from iTunes, known as M4R (.m4r).
Other Proprietary
Other companies have also introduced formats to accompany their various programs, some of which are commonly used in other programs as well. One such popular one is WMA (.wma) for Windows Media audio files and its Zune portable player. Though relatively common, WMA files cannot be played in an iPod. Sony developed a handful of formats to go with its SonicStage software and Connect Music Store, most notably ATRAC--Adaptive Transform Acoustic Coding--variations of which can have the extension .atrac, .aa3, .at3 or .oma. A similar format is RAM (.ram or .ra), which is used with the RealPlayer audio program.
Minor Formats
Other audio formats are more rare, as they are designed for specific devices and applications. Among these are AAX (.aax), developed by Audible for audiobooks, ACM (.acm), used with Interplay video games, AUP (.aup) for the Audacity audio editing and recording program, and DSS (.dss) for use with digital voice recorders. Different cell phone manufacturers also have specific formats for their voice recordings and ringtone files, including Sony Ericsson (.amr and .copy) and Nokia (.nrt and .rng).
Tags: audio files, commonly used, audio file, file format, file formats